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Biomedical subjects

C Delon-Martin

Publications and source records attributed to C Delon-Martin.

8 recordsLinked to original sources
PubMed2001

Does perception of biological motion rely on specific brain regions?

Perception of biological motions plays a major adaptive role in identifying, interpreting, and predicting the actions of others. It may therefore be hypothesized that the perception of biological motions is subserved by a specific neural network. Here we used fMRI to verify this hypothesis. In a group of 10 healthy volunteers, we explored the hemodynamic responses to seven types of visual motion displays: drifting random dots, random dot cube, random dot cube with masking elements, upright point-light walker, inverted point-light walker, upright point-light walker display with masking elements, and inverted point-light walker display with masking elements. A gradient in activation was observed in the occipitotemporal junction. The responses to rigid motion were localized posteriorly to those responses elicited by nonrigid motions. Our results demonstrate that in addition to the posterior portion of superior temporal sulcus, the left intraparietal cortex is involved in the perception of nonrigid biological motions.

Adult↗
PubMed2000

Moving illusory contours activate primary visual cortex: an fMRI study.

Identifying the cortical areas activated by illusory contours provides valuable information on the mechanisms of object perception. We applied functional magnetic resonance imaging to identify the visual areas of the human brain involved in the perception of a moving Kanizsa-type illusory contour. Our results indicate that, in addition to other cortical regions, areas V5 and V1 are activated. Activity in area V1 was particularly prominent.

Adult↗
PubMed1999

MRI measurement of the functional blood flow changes in a large superficial vein draining the motor cortex.

In this study, phase-contrast MR techniques are applied in order to measure the blood flow changes induced by a motor task in a large superficial vein draining the motor cortex. The measurements were applied to six healthy volunteers, in motor rest conditions and during performance of a motor task. The latter consisted of sequential finger-to-thumb opposition. The task was actually executed and mentally simulated. Significant blood flow increases were found when changing from from mental simulation to actual execution of the motor task (increases ranging between 1.6 and 10.3 ml/min, i.e. 9% and 45%, respectively) and from resting conditions to actual execution of the motor task (increases ranging between 1.7 and 14.0 ml/min, i.e. 32% and 72%, respectively).

Adult↗
PubMed1996

Possible involvement of primary motor cortex in mentally simulated movement: a functional magnetic resonance imaging study.

The role of the primary motor cortex (M1) during mental simulation of movement is open to debate. In the present study, functional magnetic resonance imaging (fMRI) signals were measured in normal right-handed subjects during actual and mental execution of a finger-to-thumb opposition task with either the right or the left hand. There were no significant differences between the two hands with either execution or simulation. A significant involvement of contralateral M1 (30% of the activity found during execution) was detected in four of six subjects. Premotor cortex (PM) and the rostral part of the posterior SMA were activated bilaterally during motor imagery. These findings support the hypothesis that motor imagery involves virtually all stages of motor control.

Adult↗
PubMed1995

Venous thrombosis generation by means of high-intensity focused ultrasound.

Sclerotherapy of superficial varicose veins is now performed with chemical agents since physical agents have given only poor clinical results. We investigated the possibility of using high intensity focused ultrasound energy to achieve this goal in an animal model, the rat femoral vein. A specially designed probe delivering ultrasonic energy at a central frequency of 7.31 MHz was constructed and evaluated. Femoral veins of six rats were surgically exposed to a set of between four and seven 3-s exposures at 1-mm increments at a power level of 167 W/cm2. At 2 days following the irradiation, control veins were patent while occlusive thrombus was documented by Doppler flow and histological studies in all six of the irradiated veins. No damage to the surrounding soft tissues was noted. We concluded that high-intensity focused ultrasound can be used to induce thrombosis in this animal model.

Animals↗
PubMed1995

Intracranial gradient-echo and spin-echo functional MR angiography in humans.

PURPOSE: To investigate the predominance of venous signal intensity at 1.5-T gradient-echo (GRE) functional magnetic resonance (MR) imaging of motor activity and to demonstrate the contribution from task-induced changes in flow velocity to the functional MR imaging signal intensity. MATERIALS AND METHODS: Functional MR imaging of motor activity was performed in healthy volunteers. In a first examination, conventional two-dimensional GRE blood oxygenation level-dependent (BOLD) functional MR imaging techniques were used, and the image planes were carefully positioned with respect to the veins that responded to the motor task. In a second examination, two-dimensional spin-echo (SE) techniques were used, and the image planes were oriented axially and measured in a sequential multisection manner. The areas of hyperintensity on functional MR images were eventually processed by means of maximum intensity projection. RESULTS: Functional MR angiograms were obtained in both examinations. The possibility to generate SE functional MR angiograms demonstrates that venous inflow effects may contribute substantially to signal intensity in conventional two-dimensional GRE BOLD functional MR imaging of motor activity. CONCLUSION: Veins have a substantial role in BOLD functional MR imaging of motor activity.

Adult↗
PubMed1995

[Organ cryopreservation: current status of research carried out in Grenoble].

After discussing the problem of organ cryopreservation and reviewing the current data available on this subject, the Grenoble project is presented. Physical and biological studies have been combined with experimentation of autologous renal transplantation in rabbits to assess the functional value of the retransplanted organ after treatment and cooling. Renal resistances are measured during perfusion of the kidney with the cryoprotective solution. In order to verify the homogeneity of the cryoprotector concentration in the organ, on NMR spectral imaging test has been developed. A new rapid imaging method now allows real time monitoring of concentration variations during perfusion. In addition to concentration and homogeneity, analysis of local spectra also provides information about the local temperature de the kidney.

Animals↗